We will probe the structural and transport properties of blood cells by measuring the NMR relaxation of ions, neutral solutes, hemoglobin and water. The anion transport system of red cells will be investigated through C1 and F relaxation. At low temperatures, this will reveal information on binding to the membrane transport protein, but at 38 degrees, the effect of C1 exchange should be observed, of great importance to the physiological function of CO2 removal. Proton relaxation of hemoglobin and water in red cells will be measured, using selective excitation and detection, and isotopic substitution to unravel the complex behavior of this system. The high protein concentration, and the presence of the membrane have profound effects on relaxation. Both of the above studies also give information on the osmotic properties of red cells. The content of the various cell constituants are frequently difficult to measure (e.g., water), and our experiments are done with intact cell systems.